# precalculus

find the trigonometric form of the following number:

-7 + 4i

I keep getting the wrong answer for these questions.
mine was:
square root of 65 (cos330.255 degrees + sin330.255i degrees)

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1. z = r(cos ß + i(sin ß))
where r = √(x^2+y^2)
cos ß = x/r and sin ß = y/r

your z = -7 + 4i

so r = √65, which you had correctly done

cos ß = -7/√65 and sin ß = 4/√65

the angle in standard position is 29.7┼

the quadrant where the cosine is negative and the sine is postitive is the second quadrant
so ß = 180 - 29.7 = 150.26º

so -7+4i = √65(cos 150.26 + i(sin 150.26)

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